近似线性相位全通数字滤波器的迭代重加权Minimax设计

近似线性相位是许多滤波系统希望具有的重要特性，全通滤波器则是实现这个特性的重要技术手段.提出全通数字滤波器的一种迭代重加权minimax设计方法，最小化最大加权线性相位偏差，并利用群延迟偏差信息对权函数进行迭代更新，使群延迟偏差函数近似等纹波.为展现该方法的优越性，将该方法应用于线性相位希尔伯特变换器及相位均衡器的设计.设计例子展示了算法良好的收敛性，以及在实现滤波系统近似线性相位和近似常数群延迟方面的优良性能.     

窄带线性相位微波滤波器的设计

给出了利用ADS线性仿真器和EM全波仿真器(HFSS)设计线性相位滤波器的方法．利用该方法设计了6级线性相位滤波器。实验结果和理论结果具有较好的一致性，证明了这种设计的有效性。     

基于光纤四波混频DPSK系统相位噪声提取检测和抑制

差分相移键控(DPSK）在长距离光纤通信系统中有高接收机灵敏度、高频谱效率以及抗非线性效应方面的优势,最近受到广泛关注。在DPSK通信系统中,线性相位噪声和非线性相位噪声是影响系统性能的主要因素。研究了如何利用光纤四波混频（FWM）效应来监测和抑制相位噪声,降低相位噪声对DPSK通信系统的影响。结果表明利用光纤FWM效应产物可以检测相位噪声值,并且基于光纤饱和FWM效应全光限幅器可以有效地降低非线性相位噪声,提高了DPSK系统性能。该结果对研究高速全光通信有重要意义。     

绝对编码光栅的相位细分

针对位移精密测量中提高绝对编码光栅的分辨率,提出一种绝对编码的相位细分方法。由自然码或格雷码的多码道光栅组成编码光栅,其基元码道是高频率的罗奇光栅,解码采用傅里叶变换相位计算方法,通过傅里叶变换、空间频域滤波和逆傅里叶变换得到基元码道的相位分布,利用格雷码的级次信息得到展开的相位分布。利用相位分布的线性性质进行线性拟合,实现高分辨率的相位细分。分析了实验原理并进行了提高分辨率的相位细分实验研究,实验结果表明,采用相位细分的方法,经过标定后可大大提高绝对编码光栅的分辨率和测量精度。     

晶体相位补偿网络及在线性相位滤波器中的应用

介绍一种晶体相位补偿网络,在幅频特性上,它是一种全通网络。但它能在晶体滤波器带宽范围内提供相位补偿,这样由一个普通晶体滤波器加一个晶体相位补偿器就可以组成一个线性相位晶体滤波器,同时也使线性相位晶体滤波器的设计带宽得以增加。设计更为灵活。文中也给出了一个21.85 MH z,3 dB带宽为70 kH z的线性相位滤波器的实例,其带内群时延波动≤±0.6μs。该方法可为解决滤波器幅频特性和相频特性的矛盾,提供一种新的较为灵活的折衷方案。     

FIR滤波器线性相位特性的研究

本文通过对滤波器的线性相位研究,介绍FIR滤波器的线性相位的4种特性,详细分析了FIR滤波器的线性相位的幅度特性,并在MATLAB下对FIR滤波器的4种特性进行模拟仿真实验,得到FIR数字滤波器的相位特性只取决于冲击响应的对称性.     

非局域线性研究“Snyder-Mitchell”模型研究

研究了“Snyder-Mitchell”模型的建立过程，发现模型中光束的相位被误用为非线性相位，将其改为线性相位后重建该模型。得到了只要利用光学材料的非线性特性就可证明原模型仍然成立的重要结论。     

非局域线性"Snyder-Mitchell"模型研究

研究了Snyder-Mitchell模型的建立过程,发现模型中光束的相位被误用为非线性相位,将其改为线性相位后重建该模型,得到了只要利用光学材料的非线性特性就可证明原模型仍然成立的重要结论。     

共路外差干涉测量液晶空间光调制器相位特性

为了对液晶空间光调制器进行高精度的校准, 使其满足线性相位调制的应用需求, 采用共路外差干涉法测量了液晶空间光调制器的相位调制特性, 分析了实验系统的测量原理, 取得了液晶空间光调制器相位调制量随输入灰度值变化的实验数据, 并进行了线性校准。结果表明, 实验中所用的液晶空间光调制器的最大相位调制量为2.55π, 利用反插值法对20~240灰度范围内的相位调制曲线进行线性校正后的理论相位调制曲线非常接近理想线性曲线, 相位调制曲线与理想线性调制曲线的相关系数可达0.9996;该测量方法可克服传统测量方法对图像处理的依赖性, 具有较高的测量精度, 相位调制量直接通过锁相放大器就可获得。该研究为基于液晶空间光调制器的高精度波前校正和精密测量提供了参考。     

相位测频法在雷达信号脉内特征分析中的应用

以单载频、线性调频、BPSK和FSK信号为例,通过提取信号的瞬时相位,对雷达信号的脉内调制特征进行了分析,介绍了信号瞬时相位的提取方法,然后分别引出相位分析法和相位差分分析法的调制类型识别方法,最后对这两种方法进行了仿真分析。仿真表明,相位测频法是一种有效的雷达信号调制特征分析工具。     

Simple design and realisation of linear phase 2D FIR filters withdiamond frequency support

A simple design method for linear-phase 2D FIR filters with diamond frequency support is proposed. The method is based on a 1D halfband linear-phase FIR filter design and offers some flexibility in the choice of specifications; the resulting realisation is efficient in terms of computational cost. A design example is also included     

Design of linear-phase IIR filters via impulse-response gramians

A new method for the design of a linear-phase infinite-impulse-response (IIR) filter is presented. It involves designing a finite-impulse-response (FIR) filter satisfying the given frequency response specifications and subsequently obtaining a significantly lower order IIR filter using model reduction based on impulse-response gramians. The general outline of the method and a brief overview of the existing linear-phase FIR filter design and model-reduction techniques are presented. The impulse-response gramian and the model-reduction algorithm used are presented. The method is illustrated by design examples and is compared with other methods for the design of linear-phase IIR filters using equalizers     

A design method of multidimensional linear-phase paraunitary filterbanks with a lattice structure

A lattice structure of multidimensional (MD) linear-phase paraunitary filter banks (LPPUFBs) is proposed, which makes it possible to design such systems in a systematic manner. Our proposed structure can produce MD-LPPUFBs whose filters all have the region of support 𝒩(MΞ), where M and Ξ are the decimation and positive integer diagonal matrices, respectively, and 𝒩(N) denotes the set of integer vectors in the fundamental parallelepiped of a matrix N. It is shown that if 𝒩(M) is reflection invariant with respect to some center, then the reflection invariance of 𝒩(MΞ) is guaranteed. This fact is important in constructing MD linear-phase filter banks because the reflection invariance is necessary for any linear-phase filter. Since our proposed system structurally restricts both the paraunitary and linear-phase properties, an unconstrained optimization process can be used to design MD-LPPUFBs. Our proposed structure is developed for both an even and an odd number of channels and includes the conventional 1-D system as a special case. It is also shown to be minimal, and the no-DC-leakage condition is presented. Some design examples show the significance of our proposed structure for both the rectangular and nonrectangular decimation cases     

Derivative-controlled design of linear-phase FIR filters via waveform moments

A new method for designing linear-phase finite impulse response (FIR) filters is proposed by using the blockwise waveform moments. The proposed method yields linear-phase FIR filters whose magnitude response and its derivatives to a certain order take the prescribed values at equally spaced frequency points. The design procedure only needs to solve a system of linear equations, whose size is slightly smaller than the degree of the resulting filter. In addition, the inversion of the linear equations can be essentially precomputed. Therefore, the proposed design method is computationally efficient. In particular, for some important cases, i.e., the maximally flat R-regular L/sup th/-band FIR filters, a closed-form formula can be obtained. It is also shown that the resulting R-regular L/sup th/-band FIR filters have the zero intersymbol interference property.     

具有任意正则阶的M带线性相位双正交小波构造

本文在求得尺度滤波器的前提下,利用计算代数Groebner基和合冲模的思想和算法,对多相位矩阵进行双正交化。从而得到了一种具有任意正则阶和线性相位性质的M带双正交小波的新构造方法。与现有方法相比,该方法克服了不能同时具有任意正则阶和保持线性相位的缺陷。实例表明该方法简洁、有效。     

Pseudo-QMF banks with near-equiripple performance

A novel method using the Parks-McClellan equiripple design procedure obtains a linear-phase spectral factor of an equiripple approximate 2Mth-band lowpass filter. This filter, which is an equiripple prototype of an M-channel pseudo-QMF bank, is modified to make it a closer approximation of a linear-phase spectral-factor of a 2Mth-band filter, reducing the maximum overall reconstruction error to the order of the stopband ripple, while slightly compromising equiripple performance     

Synthesis of Wideband Linear-Phase FIR Filters with a Piecewise-Polynomial-Sinusoidal Impulse Response

A method is presented to synthesize wideband linear-phase finite-impulse-response (FIR) filters with a piecewise-polynomial-sinusoidal impulse response. The method is based on merging the earlier synthesis scheme proposed by the authors to design piecewise-polynomial filters with the method proposed by Chu and Burrus. The method uses an arbitrary number of separately generated center coefficients instead of only one or none as used in the method by Chu–Burrus. The desired impulse response is created by using a parallel connection of several filter branches and by adding an arbitrary number of center coefficients to form it. This method is especially effective for designing Hilbert transformers by using Type 4 linear-phase FIR filters, where only real-valued multipliers are needed in the implementation. The arithmetic complexity is proportional to the number of branches, the common polynomial order for each branch, and the number of separate center coefficients. For other linear-phase FIR filter types the arithmetic complexity depends additionally on the number of complex multipliers. Examples are given to illustrate the benefits of this method compared to the frequency-response masking (FRM) technique with regard to reducing the number of coefficients as well as arithmetic complexity.     

基于自适应神经网络的二维线性相位FIR滤波器优化设计

提出一种基于自适应三角函数基神经网络的二维线性相位FIR滤波器优化设计方法.该方法根据二维线性相位FIR滤波器幅频响应特性,采用三角函数基神经网络优化算法计算滤波器系数,同时在神经网络训练过程引入自适应学习率算法,提高神经网络的学习效率和收敛速度.通过训练神经网络的权值,使二维线性相位FIR滤波器幅频响应与理想幅频响应...     

A method for design of Mth-band filters

The objective of this paper is to present a theory, constraints, and a design method for nonlinear-phase halfband and Mth-band filters. Based on a time-domain property, the constraints and properties in the frequency domain are derived. They are the generalization of the well-known conditions for linear-phase Mth-band filters. Having found all necessary conditions, we present the design method based on an eigenfilter that minimizes the mean-squared errors. The design method is also extended to the design of nonlinear-phase Mth-band filters with properties of R-regularity, or equiripple stopband attenuation, or impulse responses that have complex coefficients. Design examples of various Mth-band filters with different properties are presented, discussed, and compared with the linear-phase case